1. Field of the Invention
The present invention relates to heat resistant materials reinforced with silicon carbide fibers and particularly to molybdenum base composite materials reinforced with silicon carbide fibers.
Recently, molybdenum alloys have been used in the field of air craft engine, turbine, nuclear reactor materials and the like, and the demand has been increasing but at the same time, the operating conditions have become severe and the required properties have not always been sufficient in respect to the tensile strength, softening resistance and oxidation resistance at high temperatures.
2. Description of the Prior Art
It has been attempted to increase the tensile strength of the molybdenum base materials by forming solid solutions of refractory metals, such as Nb, Ta, Zr and the like, or to increase the tensile strength of the molybdenum base materials by dispersing submicron ceramic particles, such as ThO.sub.2, Y.sub.2 O.sub.3 and the like, so that the tensile strength at high temperatures, particularly the shock resistance can be endured as the structure under severe operating conditions for a long period of time, but such attempts are mechanically limited and the development of more stable reinforced materials has been demanded.
It is considered as one process for preventing the softening of molybdenum alloy at higher temperatures than the above described attempts, that whiskers of SiC and the like are embedded in said alloy to reinforce said alloy. However, the whiskers are very expensive in view of the production process and are not always stable in a metal matrix at high temperatures and when using for a long period of time, diffusion reaction occurs and the tensile strength is apt to lower.
On the contrary, silicon carbide fibers according to the present invention are continuous fibers, so that the fibers are very effective as the stress medium in metal matrix and further the fibers contain free carbon, so that the reaction of the fibers with the molybdenum matrix can be prevented even under a high temperature atmosphere and it is considered that the formed composite materials have a high useful merit in a broad field.